The present invention relates to the structure of a motive power transmission system, comprising an engine, electric motors and a gear-type transmission therein, and in particular, relates to a power transmission apparatus for obtaining both reduction of fuel efficiency (or mileage) and drivability through small-sizing and weight-lightening of the motive power transmission system.
Such the power transmission apparatus, according to the conventional art, for achieving an improvement of transmission efficiency in the motive power transmission system, as well as, the drivability thereof, is already known and described in Japanese Patent Laying-Open No. Hei 11-313404 (1999), for example.
In this publication is described the power transmission apparatus for use in an automobile, in which an input shaft of the gear-type transmission is connected to an electric power generator or alternator while an output shaft thereof is connected to an electric motor(s). With such the transmission apparatus, since various driving modes can be realized or achieved through the integrity control of the engine, the alternator, the electric motor(s), and the gear-type transmission, then it is possible to achieve the reduction in the fuel efficiency. And, compensation or adjustment is also possible for a drop in the driving power when changing over the gear trains by means of the motor(s) mentioned above, in particular, when conducting the gearshift by exchanging the gear trains through a claw clutch, and therefore, it is possible to obtain an improvement in the drivability.
For such the power transmission apparatus, it is necessary to control the engine, the electric motor(s) and the alternator, integrally, so that the engine and the electric motor(s)operate within a region of high efficiency thereof, while keeping a driver satisfy with a feeling of acceleration or deceleration that she/he requires, thereby obtaining the reduction of fuel efficiency. For that purpose, the electric motor(s) is/are connected to the output shaft of the gear-type transmission, thereby being so constructed that the reduction of driving power during the gear-shifting is adjusted by means of the electric motor(s) mentioned above.
However, with such the structure of the transmission apparatus as mentioned above, since required torque of the electric motor(s) is large during the gear-shifting, it is impossible for the electric motor(s) to escape from becoming large in the sizes thereof, and therefore it is difficult to reduce the fuel efficiency or mileage.